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Issue No. 4, Article 7/April 29, 2011

Planting Delay Lengthens: Are Decisions Needed?

According to data released by the National Agricultural Statistics Service, corn acreage in Illinois moved from 9% planted on April 17 to 10% planted on April 24. The average planted by April 24 over the past five years is 27%. It's scant comfort to the many with little or nothing planted, but Illinois is the only Corn Belt state with more than 5% of its corn planted. Iowa is 3% planted, Indiana is 2%, and Minnesota has barely started. The entire United States is only 9% planted, compared to an average of 23% by April 24.

This is disappointing after the dry start to April, but the weather pattern of storms moving across the country from the Pacific continues to hold. Rainfall totals in April so far have ranged from 4 to 5 inches in northwestern Illinois to 12 to 15 inches in the southern tip of the state. Monthly totals to date range from an inch or two above normal in the northwest to some 8 inches above normal in southern Illinois. This means that planting progress will be little or none this week, unless there are a few small areas in places that got lucky and escaped the week's downpours.

As we work to find things to occupy our time and attention during these days of delay, some have started to wonder if they should consider changing crops, from corn to soybean, or corn hybrids, from earlier to later ones. Agricultural economist Gary Schnitkey here at the University of Illinois generated a calculator to address the question of changing from corn to soybean. It uses data from some of our planting date work in Illinois, along with prices and costs, to indicate when or if we might want to make the switch. The calculator is available on the web ("Planting Decision Model").

While predicting planting date response is always somewhat uncertain, data show that losses to delayed planting accelerate sooner and faster in corn than in soybean, meaning that soybean becomes a more profitable choice at some point. At current crop prices and production costs, this will not happen until early June in Illinois. If there have already been crop-specific investments for corn, such as applying N fertilizer, there will be more incentive to stay with corn. Switching crops is certainly not a decision to rush into.

A more immediate decision that some may be considering is whether to change to an earlier hybrid, or at least to line up seed so that such a switch can be made. While some producers in northern Illinois need look back only to 2009 to find a year when later hybrids didn't do well when planted late, switching from a mid- or fuller-season hybrid to an early one means trading one set of risks for another. The first risk to be minimized for fuller-season hybrids is not having enough growing degree days to get them mature before frost. About 200 to 300 GDD accumulate in April, and the totals from April through September run from about 3,000 in northern Illinois to some 3,500 in southern Illinois. About 375, 450, and 475 GDD accumulate in May in northern, central, and southern Illinois. This means that corn planted on May 1 will experience about 2,800 GDD in northern Illinois and some 3,200 GDD in southern Illinois. This is enough to mature the fullest-season hybrids we normally grow in these regions.

If planting is delayed until June 1, the GDDs accumulated by the end of September average only about 2,450, 2,700, and 2,800 in northern, central, and southern Illinois. These are enough to mature most midseason hybrids grown in these regions, except in northern Illinois, where midseason hybrids may be rated at about 2,500 GDD or so. Research in Indiana and Ohio has shown that late-planted corn usually--but not always--requires fewer GDD than when the same hybrids are planted early. This means lower risk of not receiving enough GDD by frost for late-planted corn, but the reduction in GDD requirement is associated with yield loss, so that's not all positive.

It is clear, though, that most of the hybrids we plan to plant this year should not be switched out for earlier hybrids until and unless planting is delayed to late May or early June. Even then it's likely that first-choice hybrids may do better than those earlier hybrids we would use to replace them, especially in the southern half of the state. While bringing early--say less than 105-day RM--hybrids into the southern half of Illinois may lower risk of frost before maturity, it also means moving them from their primary area of adaptation into an area where they have not been tested or sold as first-choice hybrids. In many cases, that does not turn out very well.--Emerson Nafziger

Author:
Emerson Nafziger

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